A number of drive mechanisms adapted for transmitting rotating motion are known, and there is persistent demand for improving such drive mechanisms.
In GB 926,266 a drive mechanism is disclosed that has an input driving shaft comprising an eccentrically offset (shifted) section. A disc is connected by bearing to the eccentrically offset section of the input driving shaft such that the disc is able to rotate about the eccentrically shifted section. The disc has cylindrical through holes receiving driving-shafts secured to the housing of the drive mechanism. Upon rotation of the input driving shaft the driving-shafts guide the disc such that certain points thereof undergo a purely circular motion, and thereby the disc undergoes a so-called wobbling motion. External toothing is arranged on the periphery of the disc, by means of which the wobbling motion of the disc drives the gear-wheel, which surrounds the disc, through the internal toothing of the gear-wheel. The driven external gear-wheel is directly connected to an output driving shaft. To provide for the desired motion of the disc balance weights are secured thereto. The approach according to the document has the disadvantage that the gear-wheel driven by wobbling motion is directly connected to the output driving shaft, and thus the achievable transmission ratio range is very narrow.
In U.S. Pat. No. 4,674,361 and U.S. Pat. No. 4,958,531 rotation transmitting mechanisms are disclosed wherein an input driving shaft connected eccentrically to a plate can be applied to rotate the output driving shaft connected with an eccentrical offset to the plate at a different location. To provide the desired output driving it is required that at least one further driving-shaft is connected to the plate, also in an eccentrically offset manner. A similar approach is disclosed in U.S. Pat. No. 5,324,240.
In WO 2011/137469 A1 a drive mechanism having epicycloidal (planetary) wheel is disclosed which comprises an input driving shaft having one or more sections eccentrically shifted relative to the shaft. One or more rotatable discs are connected to the one or more eccentrically shifted sections, respectively. Internally toothed trough holes are arranged on a circumference of the disc, into which openings externally toothed epicycloidal wheels having a teeth number different from the teeth number of the openings are received. The epicycloidal wheels roll down on output gear-wheels implemented as internally threaded gears and being connected to another, also externally toothed section of the epicycloidal wheels. These portion of the epicycloidal wheels are also connected to an externally toothed gear-wheel. One of the output gears is connected to the rear wall of the drive mechanism. As can be seen also in FIG. 3c of the document, the epicycloidal wheels are not connected to this rear wall, and thereby the epicycloidal wheels are able to roll down at a given circumference of the rear wall. Accordingly, the discs are rotated with respect to the output gears upon driving the epicycloidal wheels, therefore, in the drive mechanism according to WO 2011/137469 A1 wobbling motion cannot be established on the discs, but instead other planet motion types occurring also in other planetary drive mechanisms will be realized therein.
The approach according to WO 2011/137469 A1 is mainly suitable for realizing large transmission ratios. The drive mechanism according to the document has a power flow that is unfavourable from the aspect of the value of efficiency.
In EP 291052 A2 a drive mechanism is disclosed wherein the gear-wheels roll down on a single stationary ring gear arranged coaxially with the input driving shaft, that is, the gear-wheels undergo a substantially planetary motion The pin guides utilized in this solution undergo orbital motion relative to the housing, and the angular velocity of the output driving shaft corresponds to the speed of this orbital motion.
In U.S. Pat. No. 3,129,611 a drive mechanism is disclosed that comprises multiple epicycloidal wheels arranged behind one another in an axial direction. The pins utilized in this approach undergo orbital motion relative to the housing, and the angular velocity of the output driving shaft corresponds to the speed of this orbital motion.
In U.S. Pat. No. 3,994,187, disclosing a similar approach, also planetary motion appears. In this approach the shafts comprise eccentric sections that are not secured to the housing, which, in a disadvantageous manner, greatly increases friction. A similar drive mechanism is disclosed in U.S. Pat. No. 5,655,985. A planetary-type motion appears also in EP 0551918 A2.
In DE 3810824 A1, DE 2731486 A1, U.S. Pat. No. 5,145,467, U.S. Pat. No. 4,896,567, U.S. Pat. No. 5,697,868, US 2014/0031165 A1 and U.S. Pat. No. 7,597,643 B2 drive mechanisms comprising eccentric shafts are disclosed. In WO 97/42431 A1 differential drives and transmission mechanisms comprising multiple trochoidal tooth output driving shafts are disclosed.
In light of the known solutions, there is a demand for a drive mechanism that can realize a wide range of accelerator and reduction transmission ratios gears.